Methods and apparatus for use in processing and treating particulate material

ABSTRACT

Spheres are released from within plurospheres by mixing a fluid with fly ash or bottom ash particulate material obtained by burning coal to form a slurry. The slurry is vibrated at an ultrasonic frequency and with sufficient power that plurospheres in the particulate material are cracked open to release spheres of the material which are encapsulated within the plurospheres. The so-treated material is separated from the slurry to obtain the released spheres.

This invention relates to methods and apparatus for use in processingand treating particulate material.

A process to be described below may be used, for example, to produceparticulate material of required dimensions, and in the recovery ofspecific materials, for example, metals. A further method to bedescribed below is concerned with coating particulate material.

In a particular arrangement to be described below, as an example,material contained in a slurry pulp is subjected to vibrations atultrasonic frequencies and then given a centrifugal treatment in acyclone in order to enable particles of a required size to be separatedout. A magnetic separator may be used to separate out magnetisablematerials.

In the specification of European patent application number 87306243.4,which was published under number 259959 on Mar. 16, 1998, a process andan apparatus were described for treating a flowing slurry of particulatematerial in a liquid. A plurality of ultrasonic transducers were mountedon the underside of a tray having upturned edges and the tray wassuspended by cables to facilitate vibratory flexing and undulation.Slurry flowing lengthwise down the tray was treated to a “microscopicscrubbing” by ultrasonic vibrations coupled through the tray .

In the specification of European patent application number 9111504.2,which was published under number 528070 on Feb. 24, 1993, a method andapparatus for preparing pourable bulk goods was described in which thebulk goods were all owed t o fall into a first tank where they werewashed by a liquid directed at them through nozzles to detach dirtparticles. They were then cleaned and separated in a second tank; thecleaned goods being dried and given thermal treatment by being passedthrough a pipeline system which was heated on its outside and could berotated.

The specification of French patent application number 7601726, which waspublished under number 2,338,745 on Aug. 19, 1977, disclosed a methodand device for subjecting a mixture of sand and water to irradiation byultrasonic waves from rotating transducers which were plunged into thewater-sand mixture whilst water was forced upwards through the mixture.

In the specification of Japanese patent application number 2,068,581,which was published under number 3,270,777 on Dec. 2, 1991, there wasproposed a method for treating fly ash containing a toxic substance inwhich an ultrasonic wave was applied to fly ash suspended in water toseparate the toxic materials and an ozone containing gas was bubbledthrough the suspension to decompose the toxic substance.

The removal of SO₄ from a coal ash slurry was proposed in thespecification of Japanese patent application number 870,061,344 whichwas published under number 63229189 on Sep. 26, 1988. The specificationproposed that a coal ash and water slurry be treated by ultrasonic wavesto separate water containing SO₄ and desulphurised coal ash.

Arrangements illustrative of the invention will now be described, by wayof example, with reference to FIGS. 1 to 9 of the accompanying drawingswhich show in block schematic diagrammatic form various arrangements ofapparatus and their method of operation.

Referring to FIG. 1 of the drawings, there is shown diagrammatically asilo 1 from which ash particles, which might be fly ash or bottom ashobtained by burning coal in a power station, are fed under the influenceof gravity via a conduit 2. Near to the lower end of the conduit 2, theash is mixed with water obtained via a pipe 3, and the mixture is passedinto a slurry tank 4 where it is agitated. Mixture from near to thebottom of the slurry tank 4 is fed, as indicated at 5, to a pump 6,which pumps the mixture to continuous flow chambers 7 and 8, in whichthe mixture is subjected to vibrations at ultrasonic frequencies. Theultrasonic vibrations are delivered to the mixture via horns,diagrammatically indicated at 9, and the mixture is passed via a conduit11 to a hydro-cyclone 12 for separation into particles of differingsizes. In the particular example, particles of less than 5 microns arewithdrawn via conduit 13 and particles which are larger than 5 micronsare returned from the bottom of the hydro-cyclone 12 to the slurry tank4 to be recycled and reprocessed. Or the separation (classification) ofparticles may be preferably performed dry after the drying stage asdescribed hereinafter, by using pneumatic type cyclones and airclassifiers. Typically particles are subjected to air attrition todeagglomerate particles which become agglomerated in the drying andcalcining stages as a result of alkalis that may be present in theslurry before classification. Particles can be classified into grades atsizes as small as less than 2 microns.

The mixture is passed in a continuous flow between the chambers 7 and 8via a conduit 10. The ultrasonic horns 9 are energised byelectromechanical generators 14, which are supplied with power from asource 15.

It will be appreciated that, instead of two separate flow chambers 7 and8, it is possible to employ a single flow chamber having a plurality ofultrasonic vibrators along its length, and that the means to convey thevibrations to the particulate material may be other than a horn. Forexample, it is possible for rods to extend from generators, such asthose shown diagrammatically at 14, into the moving particulatematerial, in order to cause the material to be vibrated. Other forms oftransducer, for example a plurality of frusto-conical transducerelements, arranged in line, and through which the material passessuccessively may be employed.

The applicants have found that, in one particular arrangement the use ofultrasonic vibrations in the range of 15 to 30 kHz, generated bypiezo-electric crystals and transmitted and focused in the slurry pulpby titanium disrupter horns 9, has proved particularly advantageous inproducing “cavitation”. Cavitation causes the formation and implosion ofmicroscopic vapour bubbles, and results in a shearing and tearing action(of the particle chemical or physical bonding), thus causing a greaternumber of free ultra fine fine particles in the slurry pulp.

In the arrangement mentioned above, the action is concentrated in aparticular region as a result of the design of a transducer horn and oftransducer probes, and the slurry pulp which is under treatment in thechambers 7, 8, is maintained at a pressure between 100 and 200 poundsper square inch. The particles of the desired size, which are obtainedfrom the hydro-cyclone 12, are fed via the conduit 13 to a gravity-typeunit (not shown), such as an oscillating centrifuge or flotation column,for the recovery of liberated by-products, including metal, and the mainproduct is fed to a holding tank for treatment such as dewatering anddrying (if necessary) and storage before being delivered to users.

In another arrangement to be described with reference to FIG. 2, inwhich similar components are identified by means of the same referencenumerals, a single flow chamber 7 a, which is a tubular ultrasonicirradiator, is illustrated having a plurality of ultrasonic vibrators,such as horns 9, along its length, and the output from the chamber 7 ais passed via a sump 16 and a pump 17, via the conduit 11, to thehydrocyclone 12. The power applied to the horns 9 is, in a particularmethod, between 1 and 5 kw, at a frequency of around 20 KHz.

The sonicated slurry pulp output from the hydrocyclone 12 is passed viaa conduit 13 to a second stage 2 illustrated with reference to FIG. 3.

Instead of the fly ash being delivered to the silo 1, it may, if wet, bedelivered directly to stage 2 (FIG. 3).

In a particular method, the fly ash is conveyed to the slurrytank/attrition mill 4 shown in FIGS. 1 and 2 with recycled and make-upwater for a period of 30 to 90 minutes. A dispersant, for examplestearic acid, is added continuously in small amounts, e.g. 500 to 1000parts per million. The pump 6 may be a screw/gear type non-resonatingpump.

The slurry pulp is pumped, as indicated in FIGS. 1 and 2, via conduit 11to the hydrocyclone 12 for classification at around 45 microns. Theunderflow, that is the plus 45 micron fraction, may either be recycledfor further sonication, or fed to a vacuum type filter, such as thatshown in FIG. 6, the overflow, being the minus 45 micron fraction, beinggravity fed into a gravity separator, such as a centrifuge or sonicsluice, the heavy fraction being fed to a storage container, and thelight fraction being fed to the arrangement of FIG. 4.

Referring to FIG. 3, the sonicated slurry from stage 1 (FIG. 1 or FIG.2) is shown passing via a sonic sluice 20. The heavy fraction is feddirectly to a container 21. The remainder is passed to a first lowintensity magnetic separator 22, operating at between 1,000 and 1,500gauss, from which a magnetic fraction 1 is fed to a container 23. Theremainder of the material is fed from the separator 22 to a highintensity magnetic separator 24 operating at between 5000 to 10,000gauss and the magnetic fraction which is obtained from the separator 24is stored in a container 25. From the separator 24 a light fraction ofnon-magnetic pulp is fed via a conduit 26 to a third stage whichincludes a thickener 27 from which thickened pulp is passed via aconduit 28 to a fourth stage to be described with reference to FIG. 5.Decanted effluent from the thickener 27 is passed via a conduit 29 and afilter plant 30 to the conduit 28.

Referring to FIG. 5, the thickened pulp and filtered effluent in theconduit 28 is shown being fed to a slurry tank 32, whose output ispassed via a pump 33 and a conduit 34 to a bank of hydrocyclonesconsisting of a single hydrocyclone 36, a pair of hydrocyclones 37 andfour hydrocyclones 38. A sump and a pump 39 and 40 are provided to feedthe material between the hydrocyclones 36 and 37, and a pump and sump 41and 42 are provided to feed the material between the hydrocyclones 37and 38. Coarse and medium fractions are obtained via conduits 43 and 44from the hydrocyclones 36 and 37 respectively, and from thehydrocyclones 38 there are obtained via conduits 45 and 46 fine andultrafine grades of material respectively.

These classified grades of material are passed to a vacuum filter (whichmay be of the rotary drum, filter press or other type of vacuumfiltering equipment) stage illustrated diagrammatically in FIG. 6, wherethe classified grades of pulp are shown being fed separately torespective vacuum filters 50, 51, 52 and 53, from which the vacuumedsolutions are fed via a conduit 54 to a filter plant. The filtered cakeis shown diagrammatically being passed via respective paths 55, 56, 57and 58 and decarbonizers and dryers, or burners/calciners, indicated at59, where any organic material is burnt off, to a final stage shown inFIG. 8 in which the dried graded material is shown being fed viarespective silos to bags 61-64 for the coarse, medium, fine andultrafine material.

It is possible alternatively or additionally for organic material to beburnt off at some other stage in the process, for example during thepassage of the material from the silo 1 into a calciner, such as arotary kiln type, where the exothermic energy generated from the carbonand the iron oxides that are precipitated from the flue with the ash andthe temperature of the ash itself, being 100° C. to 300° C., issufficient to power a generator to produce energy to the extent of 0.5to 2 megawatts per 2 to 4 tonnes of throughput, depending on the carbonand iron oxide content, where the carbon content can vary from 6% to inexcess of 20% and the iron oxide content from 5% to 15%. Further, asupplementary feed, such as natural gas or coal dust or waste can bemade to make up to a desired GJ/h energy balance to achieve a consistentenergy source to the generator. The resultant fly ash being ideallysuited for sale to the cement replacement concrete industry or as a feedto the process plant as described in this application.

Alternatively, depending on the fly ash which is being processed it maybe desirable to convert, with controlled heating and oxidisationconditions, the magnetite (Fe₃O₄) and or hematite (Fe₂O₃) in the ashinto highly magnetic gamma ferric oxide (FeO), which is more magneticthan magnetite and hematitite to aid in the magnetic separation, or forthe purpose of subsequently calcining the ash.

In summary, it will be understood that by using the process describedabove, ash particles may be vigorously scrubbed or polished during theirpassage through the chambers 7 and 8, enabling surface salts to beremoved and dissolved in the aqueous medium.

During the ultrasonic treatment of a slurry containing ash in thechambers 7, 7 a, and 8, the surfaces of the ash particles are cleaned,and/or partially disintegrated, preferably retaining their spheriodalshape, causing heavy metals, that had become locked in the ash particlesas a result of fusion while the material was being burnt in the furnace,to be released.

It is, moreover, possible to pre-treat the material in a slurry tank toreduce it to a pulp with a density, by weight, of between 15% to 50% ofits original density.

After treatment, magnetic separators may be used to remove certainmetallic oxides. For example, a low intensity magnetic separator may beused to remove iron oxides and paramagnetic metals may be removed usinga high intensity separator. A centrifuge may be used to capturenon-magnetic particles appearing in the conduit 13. Water that isremoved is pumped through a filtering step for recycling, or simplydischarged.

It will be understood that the resultant product may be separated outfrom the hydro-cyclone 12 (FIG. 1 and FIG. 2) at varying particle sizes,for example at 5, 10, 20, 30 or 45 microns, for use in particularrespective applications, for example as a mineral filler, extender, orpigment, a replacement for Portland cement, or a fine concrete additive.

Fly ash or bottom ash produced and treated in the ways described abovemay be used as a filler, an extender, a pigment extender, a pigment, anadditive, a replacement, a bulking agent or a viscosity agent (improver)in industrial products such as paint, coatings, plastics, resins, paper,rubber, ceramics, sealants, adhesives, concrete and other buildingproducts.

The invention also provides methods of treating particulate material,for example fly ash produced and treated in one of the above mentionedways.

It is possible to coat the surface of fly ash or bottom ash particlesproduced and treated in the ways described above with pigments andchemicals such as titanium dioxide, iron oxides, synthetic and naturalstearic acid, barium sulphate, precipitated calcium carbonate, calciumhydroxide and magnesium carbonate using ultrasonic and sonochemicaltechniques.

In one coating operation, fly ash particles produced by the processesdescribed above, which were of 0.01 microns to 100 microns in diameter,were introduced with the coating material, which was a TiO₂ pigment,into a chamber and treated by ultrasonic vibrations at a frequencybetween 15 and 40 kHz for between 1 and 120 seconds.

Other mineral materials, for example sand, may be coated using a similarultrasonic process.

It will be seen that it is possible to eliminate or at the least reducethe use of solvents in paints by employing fly ash, beneficiated asdescribed above by the removal, in particular, of materials that may bedeleterious to paint, for example unburned carbon and metallic elements.

It is believed that the reduced need for, or the elimination of, asolvent results from the fact that the beneficiated fly ash, having alow specific gravity (1.8 to 2.3 g/cm³) and spherical shape, andtherefore low bulk density (0.8 to 1.1 g/cm³), lowers the viscosity of amixture in which it is incorporated. Further, the low surface area ofbeneficiated fly ash being spherical, results in low oil demand andtherefore less vehicle/binder.

The coating of the beneficiated fly ash particles, in the way describedusing ultrasonic vibrations, improves the brightness of any mixture inwhich the coated particles are incorporated.

It will be appreciated that the particles may be coated by methodsemploying other means than ultrasonic vibrations.

A particular paint formulation, for example, employs 55-62.5% ofbeneficiated fly ash (i.e. treated using one of the processes describedabove), 10% water, 20% TiO₂ pigment and 7½-15% of a vehicle(binder/resin) e.g. oligomer. These components were emulsifiedsonically.

Reference will now be made to FIG. 9, in which there is shown a completesystem, which is similar to, but has variations with respect to thepreviously described system.

In FIG. 9, there is shown a storage silo 71 to which fly ash isdelivered directly from a power plant by a pneumatic system, by road, orby rail. The fly ash is passed from the silo 71 via a conduit 72 to aslurry tank 73 where, by the addition of hot make-up water, as indicatedat 74, and recycled water from later stages in the system, as indicatedat 75, the mixture is given a pulp density of 20% to 50% solids byweight.

The slurry tank 73 is fitted with an overflow weir, indicated at 76allowing for 2% to 5% of the slurry pulp, depending on the fly ash beingtreated, to overflow into the weir 76 for the removal of hydrophobicmaterial, such as partially oxidised coal, (unburned carbon), and hollowspheres (cenospheres) known as “floaters”, which are removed via aconduit. Slurry pulp is gravity fed or pumped from the bottom of theslurry tank 73 via a conduit 78, at a rate to equal 98% to 95% of thefeed to the slurry tank, to vibrating screens 79 fitted with one or more50 μm to 75 μm sieves for the removal of a substantial amount of theunburned carbon, (partially oxidised coal) and oversize ash particles.The oversize fraction is stockpiled for further treatment, sold as arecycled fuel source, and partially used in a later stage of the system.The undersize fraction of the slurry pulp is fed via a conduit 81 to alow intensity (500 to 1500 gauss) magnetic separator 82 for the removalof a magnetic ash fraction and discrete magnetic particles, mainlymagnetite (iron oxide), which are further stockpiled for furtherbenefication, or used or sold as a feed stock for pure ion oxide pigmentproduction, which may be used later in the process to coat the ash. Theunmagnetised fraction of the slurry pulp that is not removed by magneticforce is fed via a conduit 83 to a gravity belt type thickener 84, whereit is thickened to a pulp density of 60 to 70% solids by weight. Othertypes of thickener than a gravity belt thickener may, of course, beused. The thickened pulp is then conveyed via a conduit 85 and apositive displacement type pump 86, through a heat exchanger 87 to raisethe slurry temperature to between 100° C. to 300° C. The water that isremoved from the thickener 84 is returned via conduit 88 to the slurrytank 73.

Slurry pulp from the heat exchanger 87 is fed by a tubular connection 89to an attrition scrubber 91 in order to provide autogenous scrubbing ofparticles in the slurry to dislodge elements which have become fused tothe surface of the spheres during combustion and thus to condition theparticles to be more amenable to treatment in subsequent stages. Slurrypulp from the scrubber 91 is fed to a positive displacement pump andthence to a flow cell 93 which is fitted with ultra sonic irradiators(resonators, transducers) and is referred to as a sonicator. Power inputto the sonicator 93 from a generator 94 can be between 1,000 to 10,000kW, the sonicator frequency being typically 20 kHz. Slurry pulp beingsubjected to cavitation caused by the sonic irradiation in the sonicator94 is deagglomerated and pleurospheres, (spheres encapsulated withinspheres), are cracked releasing the encapsulated spheres, resulting insubstantial size reduction and therefore a substantial increase in theamount of the fine and ultra fine particles, (0.1 to 10 μm particlesizes). Further, chemical leaching reactions of the alkali salts andother amorphous elements are initiated. Pulp exiting the sonicator 93 isfed by a pump (not shown) to a reactor 95, which in the particularembodiment has a tube reactor consisting of coiled high pressure steeltubing being 60 cm to 180 cm in diameter and of lengths from 100 metersto 2,000 meters, depending on the desired throughput volumes andresidence times required for the dissolution of alkali salts and otheramorphous elements. Pressures of between 3 bar to 50 bar may berequired, depending on the fly ash being treated, which can be protectedfrom the effect of excess pressure being developed by the installationof pressure relief valves. Additional heating of the slurry pulp may benecessary and may be achieved by the installation of a heat exchangerwhich involves passing sections of the coiled tube of the reactor 95through a jacket containing heating oil or steam to obtain the desiredtemperatures, which may vary from 100 to 300 degrees centigrade. Thedissolution of alkali salts and other elements volatised during thecombustion step and deposited on the surfaces of the ash particles bycondensation on cooling is completed in this stage. Leach reagents maybe added, in addition to water, to the slurry pulp at this stage.

Pulp exiting the reactor 95 is gravity fed into a slurry tank 96 for theadjustment of the pulp density by means of the addition of water.Density is adjusted to 20% to 33% solids by weight.

Pulp from the slurry tank 96 is fed via a pump 97 through additionalmagnetic separators 98 and 99, the first separator 98 being a lowintensity (500 to 1500 gauss) magnetic separator, and the secondseparator 98 in series being a high intensity magnetic separator (5000to 10000 gauss) for the removal of magnetic and para magnetic particlesreleased as a result of the sonic irradiation in the sonicator 93 andhaving been made discrete as a result of being released from entrapmenton the spherical particle surface by the steps of attrition scrubbingand leaching of the alkali salts in the scrubber 91 and the leachreactor 95.

Slurry pulp is then fed into a slurry tank 101 connected to a pump 102to feed a filtering and ion exchange system 103-105. The system 103 to105 includes columns containing the oversize activated carbon separatedfrom the slurry pulp by the vibrating screens 79. A vessel containingactivated resins may be included in series in order to remove byadsorption additional elements which will be in the leach solution as aresult of prior treatment. A precipitation tank 106 may be includedafter the filtering stage 103-105 for the precipitation of alkali salts.Loaded resins and activated carbon may subsequently be treated for therecovery of adsorbed elements as by-products and alkali salts may berecovered as additional by-products.

Filtered slurry from columns 103-105 is then fed into a solid-liquidprecipitation separation and washing system 106 to achieve a cleanvitreous spherical filter cake which is conveyed to a classificationcircuit. Solution is recycled to the tank 73 via conduit 75.

Filter cake from the system 106 is reslurried in a slurry tank 107 ofthe classification circuit to a pulp density of 25% to 30% solids byweight for feeding by pumping through a series of classifiers. Theclassifiers may, for example, be either hydrocyclones or strainers.Particles are classified into medium, fine and ultra fine sizes, thetotal slurry being classified first, where a separation at between 25and 30 μm is achieved, the over size being fed to a solid liquidseparator and the undersize being fed to a secondary system for theseparation of particles at 10 μm. The resultant oversize particles arefed to a second solid liquid separator and the undersize particles arefed to a third system for separation at 3 μm to 5 μm, the oversize andthe undersize being fed to separate solid-liquid separators. The solidliquid separators are typically filter presses, rotary drum filters orcentrifuges.

In the classification circuit, the slurry is pumped via a pump 108 fromthe slurry tank 107 to a first classifier including a solid/liquidseparator backwash tank 109, which provides an output for material ofgreater diameter than 10 μm solid/liquid to a press or vacuum filter111. An output from the filter 111 is fed to drying and calcining units112 to 114 and thence to a first bagging unit 115. Filtered water isreturned to the tank 109 via a pump 116. Material having a dimensionless than 10 μm is fed from the tank 109 to a further slurry tank 117from which it is pumped via a pump 118 to a second solid/liquidseparator backwash tank 119. Particles having a size between 5 μm and 10μm are passed to a press or vacuum filter 120 from the tank 119 andthence to a second bagging unit 121 via the drying and calcining unit113. Filtered water is returned to the tank 119 via a pump 123 andparticles up to 5 μm in size are passed to a press or vacuum filter 124from the tank 119 and thence via the drying and calcining unit 114 to abagging unit 126. Input and output strainers 127 and 128 of appropriatedimensions are employed at the respective inputs and outputs of thetanks 109 and 119.

Or the separation (classification) of particles may be preferablyperformed dry after the drying stage as described hereinafter, by usingpneumatic type cyclones and air classifiers. Typically particles aresubjected to air attrition to deagglomerate particles which becomeagglomerated in the drying and calcining stages as a result of alkalisthat may be present in the slurry before classification. Particles canbe classified into grades at sizes as small as less than 2 microns.

Classified pulp is fed through a dryer and calciner system in series inorder to burn off the organic material and to oxidise occludedmagnetite, if it has not been completely removed in the precedingstages.

The separated product from the drying and calcining units may be cooledand stored in silos connected to the bagging system. Each grade may bebagged or stored in silos for bulk transport to the market, or it may befurther treated and then bagged or stored.

Certain classified and separated grades may be coated with differentcoating agents to improve the brightness and other physicalcharacteristics of the particles. Milk of lime, calcium hydroxide andcalcium oxide in solution may be precipitated from solution in a furthertreatment by the bubbling of carbon dioxide through a solution in thepresence of the vitreous ash spheres, which have activated surfaces asresult of the heat treatment, (calcining), as a precipitated calciumcarbonate (PCC). The tank used in this further treatment may besonicated accelerating the bonding of the PCC to the spherical particlesurface. Other coating agents may be used in coating the spherical ashparticles, which have been treated in the preceding stages, usingsonochemistry, such as titanium dioxide, iron oxide or other agents.

It will be appreciated that, although particular items of apparatus havebeen identified in describing the examples shown in the drawing, it ispossible to employ various alternative items of apparatus able toperform the same or similar functions in carrying out the steps of theprocess.

The methods described above for treating fly ash may be used to achievedeagglomeration, to remove surface salts and other matter on the surfaceof particulate material during and after combustion and to reduceparticle size, as well as to provide coatings on particulate material.

Although the invention has been illustrated with reference to particulararrangements, by way of example, it will be appreciated that variationsand modifications thereof, as well as other arrangements may be employedwithin the scope of the protection sought.

It will, of course, be understood that although a hydrocyclone has beendescribed as a separator or filter, any other well known separator orfilter may be used.

It will also be appreciated that, although in the particulararrangements described as examples in illustration of the invention, thefinal product has been graded or classified into particular sizes, itmay be preferred that for some applications the product should be amixture of many different sizes.

What is claimed is:
 1. A method of treating fly ash or bottom ashparticulate material obtained by burning coal including the steps ofmixing the material with a fluid to form a slurry and subjecting theslurry to vibrations at an ultrasonic frequency, the ultrasonicvibrations having such a frequency and power that plurospheres in theparticulate material are cracked open, thereby releasing spheres of thematerial which are encapsulated within the plurospheres, and separatingthe material so-treated from the slurry.
 2. A method as claimed in claim1 in which the ultrasonic vibration is in a frequency band variablebetween 15 and 30 kHz.
 3. The method of claim 1 further including thestep of classifying the material with a hydrocyclone and returningoversize material to an ultrasonic continuous flow chamber for furthercavitation, and passing on undersize material not requiring furthercavitation.
 4. The method of claim 3 further including passing theundersize material through an attrition scrubber to deagglomerate fusedparticulate material and scrubbing by attrition fused and bonded alkalisalts from the surfaces of the particulate material.
 5. The method ofclaim 1 further comprising releasing particles fused and bonded to thesurfaces of the particulate material by ultrasonic irradiation producingcavitation and by attrition scrubbing.
 6. The method of claim 1 furthercomprising releasing and removing magnetic particles present in theparticulate material before the particulate material is treated by theultrasonic irradiation step.
 7. The method of claim 1 further comprisingreleasing and removing magnetic particles present in the particulatematerial after the particulate material is treated by the ultrasonicirradiation step.
 8. The method of claim 1 further including leachingalkali salts coating the surfaces of the particulate material from thematerial in a tubular pressure reactor at elevated values of pressureand temperature.
 9. The method of claim 1 further including classifyingthe particulate material into particular range sizes by applying theparticulate material to a vibrating screen.
 10. The method of claim 1further including classifying the particulate material into particularsize ranges by subjecting the particulate material to a hydrocyclone.11. The method of claim 1 further including converting magnetite (Fe₃O₄)and/or hematite (Fe₂O₃) in the particulate material into highly magneticgamma ferric oxides under controlled heating conditions.
 12. The methodof claim 1 further including magnetically separating the particulatematerial which has been subjected to the ultrasonic vibrations to removecertain metallic oxides from the particulate material.
 13. The method ofclaim 1 further including calcining the particulate material to burn offorganic material.
 14. The method of claim 1 further including coatingthe separated material with a coating agent.
 15. The method of claim 1further including the step of magnetically separating out treatedmaterial from the slurry.
 16. Spheres released from within plurospheresby the method of claim
 1. 17. A method for use in treating fly ash orbottom ash particulate material obtained by burning coal, theparticulate material including plurospheres and the method including thesteps of mixing the material with a fluid to form a slurry, andsubjecting the slurry to vibrations at an ultrasonic frequency such thatthere is cavitation of the particulate material and the plurospheres arecracked open, thereby releasing spheres of the material which areencapsulated within the plurospheres, and leaching alkali salts coatingthe surfaces of the particulate material from the material in a tubularpressure reactor at elevated values of pressure and heat.
 18. A methodfor use in treating fly ash or bottom ash particulate material obtainedby burning coal, the particulate material including plurospheres and themethod including the steps of mixing the material with a fluid to form aslurry, and subjecting the slurry to vibrations at an ultrasonicfrequency such that there is cavitation of the particulate material andthe plurospheres are cracked open, thereby releasing spheres of thematerial which are encapsulated within the plurospheres, and calciningthe particulate material in the presence of a reducing agent, such ascarbon monoxide gas, and converting the residual particulate materialcontaining iron oxides in the form of magnetite (FeO.Fe₂O₃) and hematite(Fe₂O₃), not previously removed by magnetic separation, into gammaferric oxides, (FeO), resulting in a particulate material which issubstantially lighter in colour than it would otherwise be.
 19. A methodfor use in treating fly ash or bottom ash particulate material obtainedby burning coal, the particulate material including plurospheres and themethod including the steps of mixing the material with a fluid to form aslurry, and subjecting the slurry to vibrations at an ultrasonicfrequency such that there is cavitation of the particulate material andthe plurospheres are cracked open, thereby releasing spheres of thematerial which are encapsulated within the plurospheres, and calciningthe particulate material in an oxidising atmosphere, and the residualparticulate material containing iron oxides in the form of magnetite(FeO.Fe₂O₃), not previously removed by magnetic separation, is convertedinto hematite, resulting in a particulate material which issubstantially yellow to orange in colour.
 20. A method for use intreating fly ash or bottom ash particulate material obtained by burningcoal, the particulate material including plurospheres and the methodincluding the steps of mixing the material with a fluid to form aslurry, and subjecting the slurry to vibrations at an ultrasonicfrequency such that there is cavitation of the particulate material andthe plurospheres are cracked open, thereby releasing spheres of thematerial which are encapsulated within the plurospheres, the particulatematerial having been calcined to gamma ferric oxide, and being thereforemore magnetic than magnetite and hematite, and separating the gammaferric oxide from the residual non-magnetic fraction.
 21. A method foruse in treating fly ash or bottom ash particulate material obtained byburning coal, the particulate material including plurospheres and themethod including the steps of mixing the material with a fluid to form aslurry, and subjecting the slurry to vibrations at an ultrasonicfrequency such that there is cavitation of the particulate material andthe plurospheres are cracked open, thereby releasing spheres of thematerial which are encapsulated within the plurospheres, and calciningthe particulate material to burn off the carbon material.
 22. A methodfor use in treating fly ash or bottom ash particulate material obtainedby burning coal, the particulate material including plurospheres and themethod including the steps of mixing the material with a fluid to form aslurry, and subjecting the slurry to vibrations at an ultrasonicfrequency such that there is cavitation of the particulate material andthe plurospheres are cracked open, thereby releasing spheres of thematerial which are encapsulated within the plurospheres, during the stepof ultrasonic irradiation adding to the particulate material a coatingagent of synthetic or natural iron oxide pigments, titanium dioxide, orprecipitated calcium carbonate, the ultrasonic irradiation causing theparticles to become coated and to achieve a desired colour.